1. Field of the Invention
The present invention relates to a network device and a network system.
2. Description of Related Art
The following non-patent literature describes technologies constituting the background art in the field pertaining to the present invention: T. Matsumoto, M. Hata, M. Tanabe, K. Yoshioka, K. Oishi, “A method of preventing unauthorized data transmission in controller area network”, Vehicular Technology Conference (VTC Spring), 2012 IEEE 75th (2012). This publication describes the following issues “The CAN protocol is designed for bus networks. Each CAN message (CAN frame) has no source and no destination addresses. Therefore, every message is broadcast on a bus. Once an attacker infiltrates an ECU, he can impersonate any other ECUs on the same bus, because any ECU (node) connected to a bus can send arbitrary message. However, the CAN protocol supports no sender authentication and no message authentication.” describing issues of the CAN technologies. It proposes, as a means for addressing these issues, “a method of preventing unauthorized data transmission by leveraging the CAN's broadcasting nature. In the proposed method, the ECU to be impersonated monitors and detects the impersonated message and overrides it by sending ErrorFrame before the message transmission completes”.